With development of communications technologies, data traffic transmitted by using a wireless communications network is becoming greater. Therefore, how to improve data transmission efficiency becomes one of important technical issues in the field of communications technologies.
In the prior art, before data transmission, a radio resource control (RRC) connection needs to be established between user equipment and a base station. To reduce processing resources required for establishment of the radio resource control connection and further improve the data transmission efficiency, a method for directly sending to-be-transmitted data by the user equipment without establishing the RRC connection is provided.
However, in a data transmission process without establishing the RRC connection, when the user equipment is in idle mode, the base station releases context information (Context) of the user equipment. The context information includes information related to security authentication, encryption, and decryption. When the user equipment enters connected mode again and starts to send data, the user equipment cannot exchange the information related to security authentication, encryption, and decryption with the base station, because the radio resource control connection is not established. Consequently, the base station side cannot perform encryption and decryption related processing on the data sent by the user equipment.
In view of this, a data transmission method that enables the base station side to encrypt and decrypt the to-be-transmitted data when the RRC connection is not established is urgently required currently.